1. FIELD OF THE INVENTION
The present invention relates to an art of bonding performed in order to integrate a heat insulating material, a heating unit, and a surface cloth material in electric heaters of the type such as an electric carpet, and provides an effective heating method at the time of bonding by application of heat and pressure (this bonding operation is hereinafter abbreviated to "heat-pressure bonding").
2. DESCRIPTION OF THE PRIOR ART
A conventional method relating to the manufacture of an electric carpet comprises, as shown in FIGS. 7 and 8, wiring on a substrate, not shown, a heating wire 1 and a temperature detecting wire 2, each of which is provided on the outermost side thereof with a heat-fuseable coating layer 7, heat-pressure bonding onto the wires a bonding sheet 3 including a core material 17 having on both surfaces thereof heat-fuseable film layers 15 and 16 so as to integrate the above elements into a unit, interposing the unit between a surface cloth material 4 and a heat insulating material 5 and heat-pressure bonding these elements by means of a hot press so as to integrate these elements.
The above-mentioned hot pressing which has been conducted in the conventional method is a method which comprises interposing an object to be pressed between two hot plates, and melting and bonding the heat-fuseable film layers 15 and 16 by applying heat and pressure from the hot plates.
However, the above method suffers from the following problems. Since the heat-fuseable film layers 15 and 16 are heated by means of the hot plates and through the surface cloth material 4, the heating necessitates a long period for transmission of heat, and the surface cloth material 4 is subjected to a very high temperature which may cause discoloration. In addition, since the elements are pressed while they are at a high temperature in order to ensure positive bonding of the heat-fuseable films 15 and 16 to the surface cloth material 4 and the heat insulating material 5, the pile of the surface cloth material 4 would tend to fall out of its upright posture, spoiling its appearance, and thus causing a problem which is termed a pile-collapsing phenomenon.